As we used a different method to distort the signals (i.e., amplifying and clipping by a wave-shaping function instead of clipping at a variable threshold), the same definition of the evaluation metric would not be applicable.
For this reason, we follow the approach of [1]} and use the scale-invariant SDR (SI-SDR). It is obtained by rescaling the target signal such that the residual is orthogonal to it by using the optimal scaling factor \(\frac{\hat{s}^T s}{||s||^2} s\) :
\(\textrm {SI-SDR} = 10 \log _{10} \left( \frac{|| \frac{\hat{s}^T s}{||s||^2} s||^2}{|| \frac{\hat{s}^T s}{||s||^2} s - \hat{s} ||^2} \right),\) 
